The group of octocorals I am interested in is a family called the Chrysogorgiidae. The taxonomist Verrill (1883) stated that the Chrysogorgiidae are among “some of the most beautiful and interesting of all the known Gorgonians;” I agree! They are quite ubiquitous as they are found all over the globe, in a variety of habitats, and along a wide depth gradient (approximately 100-4000 m depth). Also, there are about a hundred described species, some generalists and some specialists in terms of habitat or depth preferences. These characteristics make the group a good model to study biogeography in the deep sea.
Among the questions I am interested in tackling using the Chrysogorgiidae are the following: is biological diversity on seamounts different from that of continental and island slopes? Is depth playing an more important role than geography in population differentiation processes? Is the deep sea a cradle or a museum of biodiversity?
Chrysogorgiid corals are also associated with a plethora of other invertebrates, notably with ophiuroids, and are therefore interesting models to study co-evolution in the deep sea. As Verrill noted, chrysogorgiids are absolutely magnificent ; if only he could have seen some of the photographs we have taken in situ with ROVs!
A GDR is a “Groupement de Recherche.” It’s a research group supported by the CNRS (Centre national de la recherché scientifique) that is meant to promote collaborative work among researchers and labs and focus on specific topics. It is meant as a way to catalyze research by helping scientists connect and share their experience. The researchers in charge of the GDR organise meetings, promote the sharing of expertise through schools, put together funding opportunities to promote collaborations, edit books toward a wider audience and special issues for academics, etc.
Tell us more about the GdRs in which you have taken part.
I have participated in two GDRs: one on Marine Connectivity and one on Environmental Genomics. Out of the former came two review papers: one was recently published in Molecular Ecology and featured in TME, the other has been submitted to Evolutionary Applications. Two special issues came out of the latter, one in Heredity and one in Genetica.
Your recent paper in Heredity (see paper here and blog post here) was the outcome of a series of serendipitous events. Briefly describe how you arrived at using NGS to describe species of octocorals (i.e., the limitations in this group of organisms, etc.).
Few molecular markers have been developed for octocorals and the majority of those markers available are mitochondrial. The mitogenome of anthozoans evolves quite slowly, to such an extant that in some groups of octocorals, we started considering mitochondrial haplotypes as representatives of putative species. In some cases, even a single mutation along a 700 nt fragment can be indicative of putative species status!
Toward the end of my PhD, I had compared morphological and mitochondrial variation within and between putative species, but had failed at developing informative nuclear markers to test the resolution of my mitochondrial data. As I started as a postdoc, the research group in Environmental Genomics published a call for proposals on the development of genomics tools for addressing questions in environmental science. We were awarded a grant to test our mitochondrial and morphological taxonomic hypotheses using RAD markers.
In the paper we published in Heredity, we tested the use of RAD sequencing to delimit species and test whether single mitochondrial haplotypes can represent species-level lineages. We found that this is true to a large extent. In addition, we presented a phylogeny for the genus, using RAD, which is interesting because few studies, to date, had used RAD in a phylogenetic context (outside of the scope of studying closely-related species).
Now that you have demonstrated congruence between RAD sequencing, morphology and mitochondrial markers, where do you go from here in describing population structure and diversity of deep sea octocorals?
Now that we have more robustly delimited species within the genus Chrysogorgia, we will go deeper into our questions in deep-sea phylogeography and biogeography. Particularly, we are interested in estimating connection among populations inhabiting different seamounts, seamount chains and island slopes. We will compare our data with other studies on deep-sea animals, such as mollusks. While we have samples from all over the world, we are focusing on the New-Caledonian EEZ and hope that our work will be useful to ongoing conservation efforts.
Thanks Eric for chatting with TME. You can see more of Eric’s research here.